Insight into intermolecular binding mechanism of apatinib mesylate and human alpha-1-acid glycoprotein: combined multi-spectroscopic approaches with in silico

Abstract

Apatinib mesylate (APM), an oral tyrosine kinase inhibitor, has a good anti-tumor activity in the treatment of various cancers, particularly in advanced non-small cell lung cancer. In this study, the intermolecular binding mechanism between APM and human alpha-1-acid glycoprotein (HAG) was investigated by combining multi-spectroscopic approaches with in silico techniques. The findings revealed that APM gave rise to the fluorescence quenching of HAG by forming a ground-state complex between APM and HAG with a stoichiometric ratio of 1:1, and APM has a moderate affinity for HAG as the binding constant of APM and HAG of approximately 10⁵ M⁻¹, which was larger than the APM-HAG complex. The findings from thermodynamic parameter analysis indicated that the dominant driving forces for the formation of the APM-HAG complex were van der Waals forces, hydrogen bonding and hydrophobic interactions, which were also verified with site-probe studies and molecular docking. The findings from in silico study indicated that APM inserted into the opening of the hydrophobic cavity of HAG, leads to a slight conformational change in the HAG, which was verified by circular dichroism (CD) measurements, that was, the beta sheet level of HAG decreased. Additionally, the results of synchronous and 3D fluorescence spectroscopies confirmed the decline in hydrophobicity of the microenvironment around Trp and Tyr residues. Moreover, some common metal ions such as Cu²⁺, Mg²⁺, Fe³⁺, Ca²⁺, and Zn²⁺ could cause the alteration in the binding constant of APM with HAG, leading to the change in the efficacy of APM. It will be expected that these study findings are to provide useful information for further understanding pharmacokinetic and structural modifications of APM.

Communicated by Ramaswamy H. Sarma

Keywords:

• Apatinib mesylate
• human α-1 acid glycoprotein
• intermolecular interaction mechanism
• spectroscopy
• in silico

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors gratefully acknowledge for the funding of Natural Science Foundation of Zhejiang province (LY19B020009) and the chemical company (KYY-HX-20210293; YX-[2016]030@; YXKF-[2005]018).